Strong yet ductile refractory high entropy alloy fabricated via additive manufacturing

Refractory high-entropy alloys (RHEA), particularly those with a body-centered cubic lattice structure, are garnering increased interest due to their potential industrial applications. However, their strength-ductility trade-off at room temperature presents a challenge that requires resolution. In this study, we fabricated a ductile Ti42Hf21Nb21V16 RHEA for additive manufacturing using a directed energy deposition (DED) technique, with a focused laser serving as the energy source. The additively manufactured RHEA demonstrated an exceptional strength-ductility synergy, boasting a gigapascal yield strength and a substantial tensile strain until failure (similar to 22.5%). Compared to its as-cast state, the tensile yield strength increased by 32%, and ductility improved slightly by 2%, suggesting a potential solution to the enduring strength-ductility trade-off dilemma. The enhanced yield strength can be attributed to solidification-enabled interstitial atoms resulting from the low-content nitrogen and oxygen atmosphere applied, while the high ductility is linked to the modified dislocation motion mechanism facilitated by the decomposition of the body-centered cubic matrix. This finding opens up possibilities for in-situ tailoring of microstructure and compositions to achieve superior mechanical performance in alloys through additive manufacturing processes.